Adolescents with atypical anorexia nervosa have higher bone mineral density (BMD) on average than adolescents with anorexia nervosa, but still experience significant deficits in fat mass index, according to study results published in the International Journal of Eating Disorders.

Estimates indicate that approximately 70% of adolescents with atypical anorexia nervosa were previously overweight. Given the rising incidence of atypical anorexia nervosa and the need for data to inform clinical guidelines, researchers compared BMD and body composition in adolescents with atypical anorexia nervosa to adolescents with anorexia nervosa and in adolescents with and without a history of overweight. Researchers reviewed electronic medical records of 286 adolescents (mean age, 15.3 years; 93% female) with atypical anorexia nervosa (n = 23) or anorexia nervosa (n = 263) who underwent clinical examination and dual-energy X-ray absorptiometry scans.

Of the total population, 46 participants reported prior history of overweight, and of these patients, 19 met the criteria for atypical anorexia nervosa.

Using linear regression models and adjusting for age, sex, and duration of illness, the researchers determined that atypical anorexia nervosa was significantly associated with greater Z-scores than anorexia nervosa for whole body bone mineral content (β, 0.88; P <.001), lumbar spine BMD (β, 0.79; P =.002), femoral neck BMD (β, 0.67; P =.009), fat mass index (β, 1.33; P =.003), and lean body mass index (β, 1.10; P <.001), but not for total hip BMD (β, 0.52; P =.054).

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Likewise, compared with no history of overweight, prior overweight history was significantly associated with greater Z-scores for whole body bone mineral content (β, 0.83; P <.001), lumbar spine BMD (β, 0.70; P <.001), total hip BMD (β, 0.53; P =.009), femoral neck BMD (β, 0.70; P <.001), and lean body mass index (β, 0.80; P <.001), but not for fat mass index (β, 0.66; P =.069).

The researchers noted several limitations to this study, including its retrospective nature and possible selection bias.

“These body composition findings are relevant to clinical practice,” the researchers said, “because they demonstrate that despite less strict weight criteria… [atypical anorexia nervosa] still captures individuals with significantly low body fat.”

Reference

Nagata JM, Carlson JL, Golden NH, Long J, Murray SB, Peebles R. Comparisons of bone density and body composition among adolescents with anorexia nervosa and atypical anorexia nervosa [published online February 16, 2019]. Int J Eat Disord. doi:10.1002/eat.23048